Fix several edge cases with context expression state

packages/babel-parser/src/parser/expression.js

@@ -950,7 +950,14 @@ export default class ExpressionParser extends LValParser {
 
   parseFunctionExpression(): N.FunctionExpression | N.MetaProperty {
     const node = this.startNode();
-    const meta = this.parseIdentifier(true);
+
+    // We do not do parseIdentifier here because of perf but more importantly
+    // because parseIdentifier will remove an item from the expression stack
+    // if function or class is parsed as identifier (in objects e.g.).
+    let meta = this.startNode();
+    this.next();
+    meta = this.createIdentifier(meta, "function");
+
     if (this.state.inGenerator && this.eat(tt.dot)) {
       return this.parseMetaProperty(node, meta, "sent");
     }
@@ -1839,8 +1846,14 @@ export default class ExpressionParser extends LValParser {
   parseIdentifier(liberal?: boolean): N.Identifier {
     const node = this.startNode();
     const name = this.parseIdentifierName(node.start, liberal);
+
+    return this.createIdentifier(node, name);
+  }
+
+  createIdentifier(node: N.Identifier, name: string): N.Identifier {
     node.name = name;
     node.loc.identifierName = name;
+
     return this.finishNode(node, "Identifier");
   }
 
@@ -1860,6 +1873,19 @@ export default class ExpressionParser extends LValParser {
       name = this.state.value;
     } else if (this.state.type.keyword) {
       name = this.state.type.keyword;
+
+      // `class` and `function` keywords push new context into this.context.
+      // But there is no chance to pop the context if the keyword is consumed
+      // as an identifier such as a property name.
+      // If the previous token is a dot, this does not apply because the
+      // context-managing code already ignored the keyword
+      if (
+        (name === "class" || name === "function") &&
+        (this.state.lastTokEnd !== this.state.lastTokStart + 1 ||
+          this.input.charCodeAt(this.state.lastTokStart) !== 46)
+      ) {
+        this.state.context.pop();
+      }
     } else {
       throw this.unexpected();
     }

packages/babel-parser/src/plugins/jsx/index.js

@@ -538,7 +538,12 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         }
       }
 
-      if (code === charCodes.lessThan && this.state.exprAllowed) {
+      if (
+        code === charCodes.lessThan &&
+        this.state.exprAllowed &&
+        this.state.input.charCodeAt(this.state.pos + 1) !==
+          charCodes.exclamationMark
+      ) {
         ++this.state.pos;
         return this.finishToken(tt.jsxTagStart);
       }

packages/babel-parser/src/tokenizer/context.js

@@ -12,30 +12,48 @@ export class TokContext {
     token: string,
     isExpr?: boolean,
     preserveSpace?: boolean,
-    override?: Function, // Takes a Tokenizer as a this-parameter, and returns void.
+    override?: ?Function, // Takes a Tokenizer as a this-parameter, and returns void.
+    generator?: boolean,
   ) {
     this.token = token;
     this.isExpr = !!isExpr;
     this.preserveSpace = !!preserveSpace;
     this.override = override;
+    this.generator = !!generator;
   }
 
   token: string;
   isExpr: boolean;
   preserveSpace: boolean;
   override: ?Function;
+  generator: boolean;
 }
 
 export const types: {
   [key: string]: TokContext,
 } = {
   braceStatement: new TokContext("{", false),
   braceExpression: new TokContext("{", true),
-  templateQuasi: new TokContext("${", true),
+  templateQuasi: new TokContext("${", false),
   parenStatement: new TokContext("(", false),
   parenExpression: new TokContext("(", true),
   template: new TokContext("`", true, true, p => p.readTmplToken()),
   functionExpression: new TokContext("function", true),
+  functionStatement: new TokContext("function", false),
+  functionExpressionGenerator: new TokContext(
+    "function",
+    true,
+    false,
+    null,
+    true,
+  ),
+  functionStatementGenerator: new TokContext(
+    "function",
+    false,
+    false,
+    null,
+    true,
+  ),
 };
 
 // Token-specific context update code
@@ -46,30 +64,44 @@ tt.parenR.updateContext = tt.braceR.updateContext = function() {
     return;
   }
 
-  const out = this.state.context.pop();
-  if (
-    out === types.braceStatement &&
-    this.curContext() === types.functionExpression
-  ) {
-    this.state.context.pop();
-    this.state.exprAllowed = false;
-  } else if (out === types.templateQuasi) {
-    this.state.exprAllowed = true;
-  } else {
-    this.state.exprAllowed = !out.isExpr;
+  let out = this.state.context.pop();
+  if (out === types.braceStatement && this.curContext().token === "function") {
+    out = this.state.context.pop();
   }
+
+  this.state.exprAllowed = !out.isExpr;
 };
 
-tt.name.updateContext = function(prevType) {
-  if (this.state.value === "of" && this.curContext() === types.parenStatement) {
-    this.state.exprAllowed = !prevType.beforeExpr;
-    return;
+tt.star.updateContext = function(prevType) {
+  if (prevType === tt._function) {
+    const index = this.state.context.length - 1;
+    if (this.state.context[index] === types.functionExpression) {
+      this.state.context[index] = types.functionExpressionGenerator;
+    } else {
+      this.state.context[index] = types.functionStatementGenerator;
+    }
   }
+  this.state.exprAllowed = true;
+};
 
-  this.state.exprAllowed = false;
+tt.name.updateContext = function(prevType) {
+  let allowed = false;
+  if (prevType !== tt.dot) {
+    if (
+      (this.state.value === "of" && !this.state.exprAllowed) ||
+      (this.state.value === "yield" && this.inGeneratorContext())
+    ) {
+      allowed = true;
+    }
+  }
+  this.state.exprAllowed = allowed;
 
   if (prevType === tt._let || prevType === tt._const || prevType === tt._var) {
-    if (lineBreak.test(this.input.slice(this.state.end))) {
+    if (
+      lineBreak.test(
+        this.input.slice(this.state.end, this.lookahead(true).start),
+      )
+    ) {
       this.state.exprAllowed = true;
     }
   }
@@ -107,8 +139,22 @@ tt.incDec.updateContext = function() {
 };
 
 tt._function.updateContext = tt._class.updateContext = function(prevType) {
-  if (this.state.exprAllowed && !this.braceIsBlock(prevType)) {
+  if (
+    prevType.beforeExpr &&
+    prevType !== tt.semi &&
+    prevType !== tt._else &&
+    !(
+      prevType === tt._return &&
+      lineBreak.test(this.input.slice(this.state.lastTokEnd, this.state.start))
+    ) &&
+    !(
+      (prevType === tt.colon || prevType === tt.braceL) &&
+      this.curContext() === types.b_stat
+    )
+  ) {
     this.state.context.push(types.functionExpression);
+  } else {
+    this.state.context.push(types.functionStatement);
   }
 
   this.state.exprAllowed = false;

packages/babel-parser/src/tokenizer/index.js

@@ -1325,14 +1325,25 @@ export default class Tokenizer extends LocationParser {
   }
 
   braceIsBlock(prevType: TokenType): boolean {
-    if (prevType === tt.colon) {
-      const parent = this.curContext();
-      if (parent === ct.braceStatement || parent === ct.braceExpression) {
-        return !parent.isExpr;
-      }
+    const parent = this.curContext();
+    if (parent === ct.functionExpression || parent === ct.functionStatement) {
+      return true;
+    }
+    if (
+      prevType === tt.colon &&
+      (parent === ct.braceStatement || parent === ct.braceExpression)
+    ) {
+      return !parent.isExpr;
     }
 
-    if (prevType === tt._return) {
+    // The check for `tt.name && exprAllowed` detects whether we are
+    // after a `yield` or `of` construct. See the `updateContext` for
+    // `tt.name`.
+    if (
+      prevType === tt._return ||
+      prevType === tt._yield ||
+      (prevType === tt.name && this.state.exprAllowed)
+    ) {
       return lineBreak.test(
         this.input.slice(this.state.lastTokEnd, this.state.start),
       );
@@ -1342,13 +1353,22 @@ export default class Tokenizer extends LocationParser {
       prevType === tt._else ||
       prevType === tt.semi ||
       prevType === tt.eof ||
-      prevType === tt.parenR
+      prevType === tt.parenR ||
+      prevType === tt.arrow
     ) {
       return true;
     }
 
     if (prevType === tt.braceL) {
-      return this.curContext() === ct.braceStatement;
+      return parent === ct.braceStatement;
+    }
+
+    if (
+      prevType === tt._var ||
+      prevType === tt._let ||
+      prevType === tt._const
+    ) {
+      return false;
     }
 
     if (prevType === tt.relational) {
@@ -1359,6 +1379,14 @@ export default class Tokenizer extends LocationParser {
     return !this.state.exprAllowed;
   }
 
+  inGeneratorContext() {
+    for (let i = this.state.context.length - 1; i >= 1; i--) {
+      const context = this.state.context[i];
+      if (context.token === "function") return context.generator;
+    }
+    return false;
+  }
+
   updateContext(prevType: TokenType): void {
     const type = this.state.type;
     let update;

packages/babel-parser/src/tokenizer/types.js

@@ -174,7 +174,7 @@ export const keywords = {
   new: new KeywordTokenType("new", { beforeExpr, startsExpr }),
   this: new KeywordTokenType("this", { startsExpr }),
   super: new KeywordTokenType("super", { startsExpr }),
-  class: new KeywordTokenType("class"),
+  class: new KeywordTokenType("class", { startsExpr }),
   extends: new KeywordTokenType("extends", { beforeExpr }),
   export: new KeywordTokenType("export"),
   import: new KeywordTokenType("import", { startsExpr }),

packages/babel-parser/test/fixtures/es2015/for-of/brackets-const/input.js

@@ -0,0 +1 @@
+for (const {a} of /b/) {}